Spark plug and method of making same



Patented Jan. 19, 1926.

UNITED STATES.

ALBERT E. SEREWICZ,

0F CHICAGO, ILLINOIS.

SPARK PLU'G. AND METHOD OF MAKING- SAME.

Application le October 27, 1919. Serial No. 333,751.

To all whom t may concern.'

' Be it known that I, ALBERT E/SEREWICZ, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented certain new and useful Improvements in Spark Plugs and Methodsof Making Same, of which the following is a specification.

. This invention relates to spark plugs such as are used in internalcombustion engines, and a method of making them, and among the objectsof my invention are to' so improve upon the structure as to reduce thepossibility of. short circuit; .to reduce the possibility of breakingthe insulation; to produce a new plug and a corresponding new methodY`of manufacture; to improve upon the construction of spark plugs ingeneral l; and to secure such further and incidental objects andadvantages as will later more fully appear.

In most prior spark plugs, the insulator, passing through 'the shell bywhich the plug is mounted in the engine, extends above the top of theshell and is therefore exposed in such a manner that it is easily brokenaccidentally. Furthermore, it is exposed to cold drafts of air and toaccidental splashing of water, as when it is necessaryto raise the hoodout of doors during a rain, and it is therefore likely to be crackedfrom one of these causes. Also, with the electrode projecting above thetop of the insulator, one is likely to vget shocks'by accidentallytouching the electrode, and this is obviated by having this partterminate within a hollow in the end of the insulator so that it isimpossible to touch the electrode when the same is live, except by usingsome tool and making a definite purposeful effort to do it. It has beencommon, though not universal practice, to secure the insulatonwithin theshell by means of a detachable ring y or gland engaging screw threadsiny or on the shell. The cutting of the threads on the shell and Aringor gland is ex uensive, and furthermore, insulators are lo ten crackedby the glands being screwed in too tightly. I have obviatedthis by mynew method of manufacture. v

When the `firing point, usually connected to the shell, is ut lntoa'hole drilled longitudinallyinto t e e'ndJof the .shell and then bentVover into proximityc to the central electrode, an entirely .SeparateOperation is involved in the drilling of the hole in the shell, it beingnecessary to remove the shell from the machine in which the threads arecut and put it into another, in which thc hole is drilled. This I haveobviated by drilling the hole transversely through the edge of theshell, which can bedone while the shell is being held stationary in themachine in which the threads are cut.

In the accompanying drawing, showing my invention, Fig., l is alongitudinal section of a completed plug provided with a central yelectrode adapted to receive any ordinary snap connector.

Fig. 2 is a longitudinal section of a completed shell before theinsulator has been applied, and 1Eig. 3 shows a plug, partly inelevation and partly in longitudinal section, provided with a centralelectrode having its external end screw-threaded for attachment of ascrew-threaded connector.

Referring more in detail to the drawing, in which'A represents theshell, B the insulator, C the central electrode, and D the connectoradapted to engage ythe external end of the electrode, 1 represents thewrench. Harige of. the shell A, and 2 the screw-threaded end, common instructures of this character. 3 is a shoulder formed within the shell,against which rests any suitable gasket 4 to cushion the insulator andform a tight joint between the shell and the insulator. 5 is a iange onthe insulator B adapted to press against the gasket l and to be engagedby an inwardly flexed art 6 of the shell A, the upper and lower aces ofthis flange being preferably inclined outwardly, although this is notnecessary.

The insulator B is made hollow at its outer end, as shownat 7, andwithin this hollow, preferably near its inner end, is the end 8 of thecentral electrode C, the shaft of which is molded in to the body of theinsulator so that it is held rmly therein, and leaves no opportunity forthe escape of gases between'the-.electrode and the insulator. As shownin Fi 1, this end 8 is provided with a ball whic may be engaged by avspring connecten', This terminal or outer end 8 may be made in variousforms to adapt it for use with any of the several standard forms ofconnector. It is shown in Fig. 3 that this end, instead of having aball, may be screw-threaded and therelos ufacture is very useful lmore,since there is a flange and the end of fore may have a screw-threadedconnector secured thereto, as shown at 10. In the latter case,'theconductor 11 Y asses down through a hollow in an insulating member, andhas it inner end spread out so that when the connector D, carrying thesleeve lO, is screwed into place, intimate contact will be causedbetween the end of the conductor 11 and the end of electrode C.

It will be observed in Fig. 2 that shell A is provided with acylindrical opening in its outer end, and that flange 9 1s connectedwith the body of the shell by a comaratively thin wall 6, so that whenthe insulator B is put into the shell and the latter; is compressedlongitudinally, the wall 6 will yield inwardl and press tightly againstthe flange 5 o the insulator, thereby pressing it tightly against thevgasket 4, and preventing an leakage of gas between these parts. It wilalso be observed) that 1n this method of manufacture, a space is leftbetween the upper end of the insulator and the flange 9, forming the topof the plug. The groove in the outer wall of the plug is turned in sucha manner as to cause the wall to flex inwardly when compressedlongitudinally and flex most sharply at the ower part, the same beingprogressivelyv 4thickened from'the thinnest portion below to the fullthickness of the flange above. In this Way a sort of metal cushion isformed whereby undue pressure caused by the press on the insulatorduring the assembling operation, is avoided. The flange 9, being longerthan the insulator, allows a. machine to be used to compress the shelllongitudinally without danger of fracturing the insulator, therebycausing a very tight fit between the insulator and its cooperatingparts. This flange 9 also prevents cold air currents from striking theinsulator as well as preventing water from splashing thereon from anyside. Furtherace between the lie insulator, this space will serve as anair jacket for the protection of the insulator.

During the Iprocess of manufacturing the shell, a hole 13 is drilledthrough the in- -ner end thereof and a pin or firing point may beinserted in this vhole to extend aV suitable distance inwardly towardthe eentral electrode C. After this pin 14 has been inserted, the metalof the shell is indented sulliciently to cause the in to be firmly heldin place. This meth of man since it permits the drilling of the hole inthe shell to be' done while the shell is held in the-machine by whichthe .thread is formed thereon without the necessity of an extraoperation, which operation, it has been (found in practice, re-Y sultsinthe breaking of numerous Vdrills because the parts are not properlyheld.

'As pointed out above, several advantages are secured by providing theflange 9, which extends outwardly far enough when the spark plug iscompleted so lthat the outer end of the insulator is entirely protectedfrom external blows and forces. It is also a considerable advantage tohave the outer end of the electrode terminating well within the outerend of the insulator and sleeve so that not only is short circuitingprevented, but. no blows can reach this electrede accidentally, therebycracking the insulator, as is so common in cases where the electrodeprojects considerably beyond the end of the insulator.

It is believed that the construction and operation of my device will beobvious from the foregoing without more detailed explanation, and it isof course understood that the specific description of the structure andAlncthods set forth above may be departed from without departing fromthe spirit of my inventiop as set forth in this specification and theappended claims.

Having now described my invention, l claim:

l. A spark plug comprising longitudi` nally apcrtured body and flangedportions, an insulator` therein and having a flange, said body portionhaving a shoulder for the flange of the insulator, said body and flangeportions being connected by a part which is thinner than the flange,said part`r flange connected to the said inwardly bent portion andextending outwardly beyond the end of the insulator.

A spark plug having a longitudinally apertured shell providedintermediate its ends with a shoulder, a flanged insulator .pressingagainst said shoulder, the said shell having a flange connected to thebody thereof by a relatively thin portion flexed inwardly to pressagainst the flange of thel insulator, thereby holding the sarle inposition, said insulator having a hollow outer end terminating withinthe outer end of the flange and separated therefrom by an air 4. A sparkplug-having a longitudinally apertured shell'provided intermediate itsends with a shoulder, ,a5 flanged insulator pressing against saidshoulder, the said shell having a iange connected to the body thereof bya relatively thin portion flexed i -body portion having an internalshoulder,

inwardly to press against the flange of the insulator, thereby holdingthe same in position, said insulator having a hollow outer endterminating within the outer end of the flange on the shell, andseparated therefrom by an air space, said insulator being providedhwithav longitudinally disposed electrode terminating inwardly near the innerextremity of the shell and terminating outwardlywithin the hollow in theend of the said insulator.

5. The method of making a spark plug i comprising forming an aperturedshell with aflexible portion intermediate the ends of the shell whichportion is thinnerthan the iange', placing a flanged insulator in'saidshell with the flange of the insulator seated upon a shoulder formed inthe shell, longitudinally compressing the shell to cause an inwardflexing of the intermediate rela-V 'shoulder for the flange of theinsulator.

6. A spark plug comprising an apertured an insulator located in saidbody portion and seated on saidshoulder, an apertured ianged portionconnected to said body portion by a flexible portion which is thinnerthan the flange, said flexible connecting por.- tion extending inwardlyinto contact with insulator for forming a second shoulder therefor.

7 A spark plug comprising a shell, an insulator mounted in the shell andhaving its outer end terminating Within the outer end of the shell, saidshell having a thin Wall portion intermediate the ends of the shell andcapablewhen the shell is longitudinally compressed to flex into tighten-l gagement with the insulator.

In wit-ness whereof; I hereunto subscribe my name to this specification.

ALBERT E. SEREWICZ.

